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Agenda and Objectives

Trane Engineers Newsletter Live Series

High-Performance VAV Systems

Variable-air-volume (VAV) systems have been used to provide comfort in a wide range of building types and climates.

This course will discuss design and control strategies that can significantly reduce energy use and ensure proper

ventilation in VAV systems. Topics will likely include: ventilation system design and control, optimized VAV system controls,

cold air distribution, and other energy-saving strategies.

By attending this ENL you will be able to:

1. Summarize ASHRAE Standard 189.1 requirements for a VAV system

2. Explain how to implement optimized VAV system control strategies

3. Summarize how to design and control cold-air VAV systems

4. Apply air-to-air energy recovery in a VAV system

Agenda

1) Opening (welcome, agenda, introductions)

2) What does ASHRAE 189.1 (or the IGCC) require for a VAV system?

3) Optimized VAV system controls

a) Optimal start/Optimal stop

b) Fan-pressure optimization

c) Supply-air-temperature reset

d) Ventilation optimization

3) Cold-air Distribution

a) Benefits

b) Tips to maximize energy savings

c) Minimizing comfort problems due to cold air “dumping”

d) Avoiding condensation on air distribution system components

4) Air-to-air energy recovery

5) List of other energy-saving strategies (RTVAV and CHWVAV)

6) Share results of example TRACE analyses

4) Summary

Agenda_APPCMC042.ai 1 6/17/2014 11:15:26 AM

Presenters

Trane Engineers Newsletter Live Series

High-Performance VAV Systems (2011)

Dennis Stanke | staff application engineer | TraneWith a BSME from the University of Wisconsin, Dennis joined Trane in 1973, as a controls development engineer. He is now a Staff Applications Engineer specializing in airside systems including controls, ventilation, indoor air quality, and dehumidification. He has written numerous applications manuals and newsletters, has published many technical articles and columns, and has appeared in many Trane Engineers Newsletter Live broadcasts.

An ASHRAE Fellow, he currently serves as Chairman for ASHRAE Standard 189.1, Standard for the Design of High-Performance Green Buildings Except Low-Rise Residential Buildings. He recently served as Chairman for ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air Quality, and he served on the USGBC LEED Technical Advisory Group for Indoor Environmental Quality (the LEED EQ TAG).

John Murphy | applications engineer | TraneJohn has been with Trane since 1993. His primary responsibility as an applications engineer is to aid designengineers and Trane sales personnel in the proper design and application of HVAC systems. As a LEED AccreditedProfessional, he has helped our customers and local offices on a wide range of LEED projects. His main areas ofexpertise include energy efficiency, dehumidification, dedicated outdoor‐air systems, air‐to‐air energy recovery,psychrometry, and ventilation.

John is the author of numerous Trane application manuals and Engineers Newsletters, and is a frequent presenteron Trane’s Engineers Newsletter Live series of broadcasts. He also is a member of ASHRAE, has authored severalarticles for the ASHRAE Journal, and is a member of ASHRAE’s “Moisture Management in Buildings” and“Mechanical Dehumidifiers” technical committees. He was a contributing author of the Advanced Energy DesignGuide for K‐12 Schools and the Advanced Energy Design Guide for Small Hospitals and Health Care Facilities, andtechnical reviewer for The ASHRAE Guide for Buildings in Hot and Humid Climates.

Biographies_APPCMC042.ai 1 6/17/2014 11:14:31 AM


Ingersoll Rand

© 2011 Trane, a business of Ingersoll-Rand2

High-Performance VAV Systems Course ID: 0090005954

1.5

Trane Engineers Newsletter Live Series High-Performance VAV Systems

©2011 Trane a business of Ingersoll Rand 3

“Trane” is a Registered Provider with The American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members Certificatesreported to CES Records for AIA members. Certificates of Completion for non-AIA members are available on request.

This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or


product.

Copyrighted Materials

This presentation is protected by U.S. and international i h l R d i di ib i di l dcopyright laws. Reproduction, distribution, display, and

use of the presentation without written permission of Trane is prohibited.

© 2011 Trane, a business of Ingersoll-Rand. All rights reserved.





Today’s Topics

ASHRAE 189.1 requirements

Optimized VAV system controls

Cold-air distribution

Air-to-air energy recovery

Other energy-saving strategies

Energy modeling results

Summary


Summary

Today’s Presenters


Dennis Stanke

Staff ApplicationsEngineer

John Murphy

Applications Engineer



ASHRAE Standard 189.1-2009

What does the “high fperformance green

building” standard require in a “high performance VAV system?

For commercial, institutional and hi rise


institutional, and hi-rise residential buildings, the standard covers …

Std 189.1-2009 HPGB Provisions

Site sustainability: e.g., site location, heat island rainwaterheat island, rainwater

Water use efficiency: e.g., turf, fixtures, once-through, condensate recovery

Energy efficiency: Std 90.1 compliance plus…

Indoor environmental quality (IEQ): e.g., Std 62.1 all sections, plus OA sensing and no smoking, Std 55 compliance, acoustics, daylighting


Atmosphere, materials and resources: e.g., recycle, reuse, no CFC’s allowed

Construction and plans for operation



Std 189.1-2009 and high performance VAV HPGB VAV-Specific Provisions

Optimized VAV controls

Cold air distribution• Energy performance modeling shows value of HP VAV

cold air distribution



Energy Requirements

Std 189.1-2009 Provisions 90.1-2010

Topic 90.1-2007 Plus 189.1-2009

Optimal start/stop controls

6.4.3.3.3 Controls must automatically adjust start time for 10,000 cfm air

No additional requirements (i.e., sameas 90.1-2007)

Same as 189.1-2009

handlers, based on space temperature, occupied setpoint and time prior to occupancy

Fan pressure optimization

6.5.3.2 Prescriptiveoption must reset supply static pressure lower to keep one zone damper nearly wide open

No additional requirements (i.e., sameas 90.1-2007)

Same as 189.1-2009

Supply air temperature No mandatory or No mandatory or 6.5.3.4 Prescriptive


pp y preset

yprescriptive requirements

yprescriptive requirements

poption must reset supply air temperature by approximately 5°F

Demand controlled ventilation

6.4.3.9 Must use DCV in zones >500ft2 with >40 people/1000 ft2

7.4.3.2 Prescriptive option must include DCV in zones >500 ft2 with ≥25 people/1000 ft2

6.4.3.9 Must use DCV in zones >500ft2 with >40 people/1000 ft2



Energy Requirements

Std 189.1-2009 Provisions 90.1-2010

Topic 90.1-2007 Plus 189.1-2009

Ventilation reset control No mandatory or prescriptive requirements

No mandatory or prescriptive requirements

6.5.3.3 Prescriptive option must reset VAVsystem OA intake based on system ventilation efficiency

Cold-air distribution No mandatory or prescriptive requirements

No mandatory or prescriptive requirements

Same as 189.1-2009


6.5.6.1 Prescriptive option must recover enthalpy with ≥50% effectiveness in systems with ≥5000 cfm and OA

7.4.3.8 Prescriptive option must recover enthalpy with ≥60% effectiveness in systems ranging from 1000 to

6.5.3.4 Prescriptive option must recover enthalpy with ≥50% effectiveness in systems ranging from 1000 to


≥70% of design supply air

g g30,000 cfm and OA ranging from 10% to 80% of design supply air

g g26,000 cfm and OA ranging from 30% to 80% of design supply air


OptimizedSystem Controls




Today’s Topics







Summary


Summary

Optimal start/stop

Optimized VAV System Controls

• Time-of-day scheduling

Fan-pressure optimization

Supply-air-temperature reset

Ventilation optimization • Demand-controlled ventilation (DCV)

at the zone level


• Ventilation reset controlat the system level (TRAQ dampers)



Optimal Start

systemon

systemoffoccupied hourson offoccupied hours

occupiedheating

setpoint

unoccupiedheating

optimalstart


6 AM noon 6 PMmid mid

gsetpoint

Optimal Stop

systemon

systemoffoccupied hourson offoccupied hours

optimalstop

drift belowoccupied

occupiedheating

setpoint

unoccupiedheating


6 AM noon 6 PMmid mid

occupiedsetpoint

gsetpoint



Time-of-Day Scheduling

Avoid overly-conservative scheduling by i l di ti d id b ttincluding a timed override button on zone sensors

Use separate schedules for areaswith differing usage patterns






measured energy savings for a small school district

Proper Scheduling, Night Setback

15,000,000 250,000Energy savings

Utility cost savings

En

erg

y sa

vin

gs

(kB

tu) 14,000,000

13,000,000

12,000,000

11 000 000

200,000

150,000

100,000

50 000

Utility co

st saving

s ($)



year one year two year three year four

11,000,000

10,000,000

50,000

0



measured energy savings for a government office building

Proper Scheduling, Night Setback

2,500,000 25,000

2,000,000

1,500,000

1,000,000

500 000

20,000

15,000

10,000

5 000

Energy savings


En

erg

y sa

vin

gs

(kB

tu) U

tility cost savin

gs ($)


year one year two

500,000

0

5,000

0


Optimal start/stop• Time-of-day scheduling



Ventilation optimization • Demand-controlled ventilation at zone level

• Ventilation reset at system level (and TRAQ dampers)


Ventilation reset at system level (and TRAQ dampers)



Traditional VAV Fan Control

VAV boxes

supplyfan

PP

static


pressuresensor

staticpressure

Fan-Pressure Optimization

pressuresensor

supplyfan

PP


communicating BAS

VAV boxes



surge

fan-pressure optimization

Part-Load Energy Savings

stat

ic p

ress

ure duct static pressure

control

1 i


airflow


1 in.wc.

siti

on

Room 204

zon

e V

AV

dam

per

po

s




Room 200

Room 201

Room 202

Room 203

Room 204


Room 205

staticpressure

Fan-Pressure Optimization

pressuresensor

supplyfan

PP


communicating BASVAV boxes




Benefits

Part-load energy savings

Lower sound levels

Better zone control

Less duct leakage

Reduced risk of fan surge

Factory-installation and -commissioningof duct pressure sensor


of duct pressure sensor

Operator feedback to "tune the system"





Ventilation optimization • Demand-controlled ventilation (DCV)

at the zone level


• Ventilation reset control at the system level (TRAQ dampers)



Supply-Air-Temperature (SAT) Reset

Benefits

• Decreases compressor energy

• More hours when economizer provides all necessary cooling (compressors/chiller shut off)

• Decreases reheat energy

Drawbacks

• Increases fan energy


• Increases fan energy

• May raise humidity level in zones

SAT reset

General Principles

First reduce supply airflow• Significant energy savings

from unloading the fan

Raise SAT setpoint when it canenhance airside economizingand/or reduce reheat energy




SAT reset based on VAV damper positions

Example #1

SAT

i ti BAS VAV boxes

pressuresensor

supplyfan PPTT

SATsensor


communicating BAS VAV boxes

First, reduce duct SP to minimum limit.

Then, raise SAT setpoint.

SAT reset based on VAV damper positions

Example #1

Benefits of this approach• Maximizes fan energy savings by waiting until you have

reset the duct SP as low as possible before you raise the SAT setpoint

• Ensures that no zone is over-heated (starved for air)

Drawbacks of this approach• SAT setpoint may not get reset upward very often,


so might not have much impact on reheat energy use Cooling load in every zone needs to be low enough that all

VAV dampers are partially closed, even when duct SP setpoint is at minimum



SAT reset based on OA temperature

Example #2

F 61te

mp

erat

ure

set

po

int,

ºF

60

59

58

57

56


50 55 6045 757065

outdoor dry-bulb temperature,ºF

SA

55


Example #2 When OA temperature > 65°F, no SAT reset

• When it is this warm outside, the economizer has not likely been activated yet and the cooling load in most zones is likely high enough that reheat is not yet required to prevent overcooling

• Takes advantage of significant energy savings from unloading supply fan

• The colder (and drier) supply air allows the system to provide sufficiently dry air to the zones, keeping indoor humidity levels lower

When OA temperature < 65°F, reset SAT upward (max SAT limit of 60°F)

• Supply fan is likely significantly unloaded by this point

• Increases benefit of airside economizer, allows compressors to shut off sooner

• Reduces any reheat required to prevent overcooling the zones

• Outdoor air is less humid so the risk of elevating indoor humidity by providing ( d tt ) l i i l d


warmer (and wetter) supply air is lessened

Limiting SAT reset to 60°F allows the system to satisfy cooling loads in interior zones without needing to substantially oversize VAV terminals and ductwork

Disable SAT reset when outdoor dew point is too high (e.g. above 60ºF or 65ºF) or when indoor humidity is too high (e.g. above 60% or 65% RH)




Example #2

Benefits of this approach• Achieves fan energy savings by waiting until it is cool

outside before raising the SAT setpoint

• May achieve more reduction reheat energy by not waiting for duct SP to be reset to minimum

Drawbacks of this approach• “Open loop” control does not ensure that a zone is not


over-heated (starved for air)

SAT reset based on OA temperature and VAV damper positions

Example #3

F 61

tem

per

atu

re s

etp

oin

t, º

F

60

59

58

57

56

reset based onworst-case

zone


50 55 6045 757065

outdoor dry-bulb temperature, ºF

SA

55



SAT reset based on OA temperature and VAV damper positions

Example #3

Benefits of this approach• Achieves fan energy savings by waiting until it is

cool outside before raising the SAT setpoint

• May achieve more reduction reheat energy by not waiting for duct SP to be reset to minimum

• Ensures that no zone is over-heated (starved for air)

Drawbacks of this approach


• Both sequences use the same input signal(position of the furthest-open VAV damper), so they require careful coordination

SAT reset

Humidity Override

BAS

RH

lounge restroom

storage office

rs

vestibule corridor

RH RH


office conference room computer roomreception area elev

ato

r



SAT reset

Application Considerations

Will compressor and reheat energy savings outweigh additional fan energy?outweigh additional fan energy?

Consider impact on zone humidity

Design zones with nearly-constant coolingloads for warmer (reset) SAT • May require larger VAV terminals and ductwork

• Allows SAT reset while still providingd d li t th


needed cooling to these zones

Design an efficient air distribution system• Employ fan-pressure optimization





Ventilation optimization (dynamic reset)• Demand-controlled ventilation at zone level

• Ventilation reset at system level (and TRAQ™


Ventilation reset at system level (and TRAQ dampers)



dynamic reset approaches – zone level

Demand Controlled Ventilation (DCV)

Estimate current population (Pz) based on:1. Time-of-day schedule (e.g., when a class is in

session)

2. Occupancy sensors (e.g., motion detectors)

3. Actual sense population (e.g., using turnstiles, ticket sales, and so on, or changes in CO2 levels)

Find required breathing zone OA flow (Vbz) using ti t d l ti


estimated population

Alternatively: 4. CO2-based: Estimate required breathing zone OA flow

(Vbz) directly based on CO2 levels

Estimate the current OA flow required using CO2

l l

dynamic reset approaches – zone level

Demand Controlled Ventilation (DCV)

levels• Steady state concentration equation

(Cr –Co) = k*m/(Vbz/Pz)

• Typical straight-line proportional controller

Vbz = slope*CO2 + offset




dynamic reset approaches – system level

Outdoor Air Intake Flow w/DCV

For single zone systems:Vot = Vbz/Ez

For 100% zone systems:Vot = all zones(Vbz/Ez)

For multiple-zone systems:Vou = (Rp*Pz) + (Ra*Az)

Zdzcritical zone = Vbz/Vdz


Zdzcritical zone Vbz/Vdz

Ev = 1 + Vou/Vps – Zdzcritical zone

Vot = Vou/Ev

dynamic reset approaches – zone/system level

Ventilation Reset Control air-handling unit withflow-measuring OA damper

Reset outdoor airflow

SA RA


Required ventilationActual primary airflow (flow ring)

DDC VAV controllerscommunicating BASNew OA setpoint

…per ASHRAE 62




CO2 Sensor in Every Zone?communicating BAS

lounge restroom

storage office

rs

vestibule corridor

CO2 CO2AHU


office conference room

computer roomreception area e

levato

r

CO2CO2

CO2 CO2

CO2 sensor in every zone

Drawbacks

Requires a CO2 sensor in every zone • Increases installed cost and maintenance

• Unnecessary use of sensors (CO2 level doesn’t change much in many of the zones, non-critical zones will always be over-ventilated)

• Increases risk of over-ventilating or under-ventilating

Requires BAS to poll all sensors to determine OA d iti


damper position

Requires some method to ensure minimum outdoor airflow




Zone DCV with Ventilation Reset Control communicating BAS

lounge restroom

storage office

s

vestibule corridor

CO2 OCCAHU


office conference room

computer room

reception area

ele

vato

rs

CO2OCC

TOD TOD

air-handling unit withflow-measuring OA damper

Reset outdoor airflow


Zone DCV with Ventilation Reset Control

SA RA


CO2 OCC OCC

Required ventilation (TOD, OCC, CO2)Actual primary airflow (flow ring)

DDC VAV controllerscommunicating BASNew OA setpoint

…per ASHRAE 62

CO2TOD TOD



ventilation optimization

Benefits

Saves energy during partial occupancy

Lower installed cost, less maintenance, and more reliable than installing a CO2 sensor in every zone• Use zone-level DCV approaches where they best fit

(CO2 sensor, occupancy sensor, time-of-day schedule)

• Combine with ventilation reset at the system level


“Occupied Standby” Mode

Use an occupancy sensor to:• Shut off lights

• Raise/lower zone temperaturesetpoint by 1ºF or 2ºF

• Reduce outdoor airflow requirement

• Lower minimum airflow settingto reduce or avoid reheat




occupied standby mode

Example

1000-ft2 conference room(d i 50)(design occupancy = 50)

Lights on off

Zone cooling 75ºF 77ºFsetpoint

Outdoor airflow 310 cfm 60 cfm

occupiedmode

occupied standbymode


required (Rp Pz + Ra Az) (Ra Az)

Minimum primary 450 cfm 225 cfmairflow setting

outdoor airflow sensing

Traq™ Damper/Sensor Assembly

A damper assembly that …Controls airflo b• Controls airflow by modulating a set of round dampers

• Measures airflow at all conditions (as required indirectly by Std 62.1 and Std 90.1, and as required explicitly by Std 189 1


explicitly by Std 189.1 and for a LEED credit)




Damper Assembly

Uses proven flow-sensing technology

• Flow ring senses differential (total inlet to “wake” outlet)

pressure), which can be very low

• Air doesn’t enter sensing ports, so filtration isn’t needed

• Transducer auto-calibrates once each minute, to correct for drift due to temperature changes


for drift due to temperature changes

• Bell mouth inlet directs air across flow ring to reduce turbulence and pressure drop


Damper Assembly

AccuracyTested in accordance ith AMCA 610 “Airflo• Tested in accordance with AMCA 610 “Airflow Measurement Station Performance”

• ± 5% of actual airflow• Precision maintained from 100% down to 15% of

nominal (design) flow (or down to 5% in some configurations)

Damper leakage


Damper leakage

• “Low leak” class• Meets Std 90.1 requirements




Damper AssemblyFor a #25 air-handling unit, 12,500 cfm

Device ΔP in. wc.

Inlet Velocity

Traq™ 0.30 1,900 fpm

Blade assembly:

Filter 0.39

Sensor 0.00

Damper 0 25


Damper 0.25

Total Assembly 0.64 1,200 fpm

Example TRACE® 700 Analysis


Optimal start


Supply-air temperature reset

Ventilation optimization • DCV at zone level

• Ventilation reset at system level


• Ventilation reset at system level



VAV system

Energy Savings Via Optimized Controls100

ase

9% 11%17% 18%

20

40

60

80

C e

ner

gy

use

, % o

f b

a


0

20

HV

AC

Houston Los Angeles Philadelphia St. Louis

typical VAV system with optimized controls

typical VAV system


Cold AirDistribution




Today’s Topics







Summary


Summary

Lower Supply-Air Temperature

Benefits Reduces supply airflow

• Less supply fan energyand less fan heat gain

• Smaller fans, air handlers,VAV terminals, and ductwork

Lowers indoor humidity levels

Drawbacks


Drawbacks Fewer economizer hours

Increased reheat energy



lower supply-air temperature

Maximize Energy Savings

Use supply-air temperature reset during mild weather• Maximizes benefit of airside economizer

• Reduces reheat energy use


Impact of SAT on Reheat Energyprimary air

55ºF

design primary airflow = 1000 cfmminimum primary airflow = 300 cfm

(30%) reheat activated when space coolingload drops below 30% of design

primary air48ºF


design primary airflow = 740 cfmminimum primary airflow = 300 cfm

(40%) reheat activated when space coolingload drops below 40% of design



design(1000 cfm)

m

heating coil activated(48ºF SAT t )

heating coil activated(55ºF SAT system)

s

85

minimum(300 cfm)

pri

mar

y ai

rflo

w, c

fm

design(740 cfm)

(48ºF SAT system)

sup

ply-air tem

peratu

re, ºF

55

65

75

extra reheat energybut not if SAT reset is used


space loaddesign

cooling loaddesign heating load

45

but not if SAT reset is used



Use supply-air temperature reset during mild weather

Raise space setpoint by 1ºF or 2ºF• Lower indoor humidity often allows zone dry-bulb temperature

to be slightly warmer

• Further reduces airflow and fan energy use







Raise space setpoint by 1ºF or 2ºF

Keep same size ductwork• Further reduces fan energy use

• Allows SAT reset in systems that serve zones with near-constant cooling loads

• Capable of delivering more airflow if loads increase in the future


loads increase in the future

chilled-water VAV system

Example Office Building (Tampa)

100%

110%

% o

f b

ase

70%

80%

90%

VA

C e

ner

gy

con

sum

pti

on

, %


60%

HV

55ºFsupply air

48ºFsupply air

smaller ducts

raisespace

setpointby 1ºF

SAT reset48ºF

to55ºF

48ºFsupply air

same size ducts

raisespace

setpointby 1ºF



High-Velocity Round Ductwork

round duct6700 cfm at 45ºF


rectangular duct10000 cfm at 55ºF2000 fpm

4000 fpm




Raise space setpoint by 1ºF or 2ºF

Keep same size ductwork

Use parallel fan-powered VAV terminals• Reduces reheat energy use by recovering heat

from warm air in ceiling plenum





Challenges

Minimize comfort problems d t “d i ”due to “dumping”

Avoid condensation on air distribution system components



Minimizing Comfort Problems (Dumping)

Use linear slot diffusers

linear slotdiffuser

“dumping”

conventional concentric diffuser


Implement supply-air-temperature reset

diffuser concentric diffuser




Minimizing Comfort Problems (Dumping)

…or use fan-powered VAV terminals as “air blenders”

primary air (45ºF)

plenum air (80ºF) primary air

(45ºF)


parallel fan-poweredVAV terminal

supply air (55ºF)

series fan-poweredVAV terminal

supply air (55ºF)

plenum air (80ºF)


Avoiding Condensation

Properly insulate and vapor-seal d t k VAV t i l d l i diffductwork, VAV terminals, and supply-air diffusers




surface temperatures on duct insulation (wrapped metal duct)• 44ºF supply air (Trane district office in Dallas, TX)• fully-ducted return air path (85ºF dry bulb above ceiling)

trunk duct (2 in. insulation)outer surface temp = 82ºF


p

branch duct (1 in. insulation)outer surface temp = 77ºF


Avoiding Condensation

Properly insulate and vapor-seal d t k VAV t i l d l i diffductwork, VAV terminals, and supply-air diffusers

Use an open ceiling plenum return, if possible

Maintain positive building pressure to reduce infiltration of humid outdoor air

Use linear slot diffusers to increase air motion

Monitor indoor humidity during unoccupied periods


Monitor indoor humidity during unoccupied periods and prevent it from rising too high

During startup, slowly ramp down the supply-air temperature to pull down indoor dew point



examples

Humidity Pull-Down Sequence

SAT ramp-down schedule

SAT ramp down based on indoor dew point

supply airflow supply-airlimit temperature

2 hours before occupancy 40% of design 55ºF

1 hour before occupancy 65% of design 51ºF

Scheduled occupancy no limit 48ºFSource: ASHRAE Cold Air Distribution System Design Guide (pp 138-140)


SAT ramp-down based on indoor dew pointex: SAT = current indoor dew point – 3ºF


Air-to-AirEnergy Recovery




Today’s Topics







Summary


Summary

Air-to-Air Energy Recovery

total-energywheel

EAEA


OAOA



Air-to-Air Energy Recovery

Benefits Drawbacks

Reduces cooling, dehumidification, heating, and humidification energy

Allows equipment downsizing

Increases fan energy

Requires exhaust air be routed back to the device


air-to-air energy recovery

Considerations for VAV Systems

Size energy-recovery device for minimum outdoor i fl i d t i i i flairflow required, not economizing airflow

Strive for balanced airflows

Ensure that the device is controlled properly• Turn off during mild weather to avoid wasting energy

• Provide a means of capacity control during heating

• Include bypass dampers for airside economizing


yp p g



Miami, FL(Mon - Fri, 6 AM - 6 PM)

wheel on (2560 hrs)


wheel off (560 hrs)

St. Louis, MO(Mon - Fri, 6 AM - 6 PM)

wheel on (1070 hrs)

wheel on,heating


wheel off (1473 hrs)

(577 hrs)




Capacity Control During Heating

RARAEAEA7000 cfm

30ºF 63ºF

70ºF

8000 cfmwheel on at

full capacitycooling coil on


SASAOAOA10000 cfm

18000 cfm55ºF

30ºF

66ºF

63ºF (66ºF to 55ºF)


Capacity Control During Heating

RARAEAEAbypass damper

7000 cfm

30ºF 43ºF

8000 cfmwheel on at

partial capacity

both coils off

70ºF


OAOA

18000 cfm

30ºF

55ºF

43ºF both coils off

SASA55ºF10000 cfm




Considerations for VAV Systems

Size energy-recovery device for minimum outdoor i fl i d t i i i flairflow required, not economizing airflow

Strive for balanced airflows

Ensure that the device is controlled properly• Turn off during mild weather to avoid wasting energy

• Provide a means of capacity control during heating

• Include bypass dampers for airside economizing


yp p g

Provide a method for frost prevention in cold climates


Other Energy-Saving Strategies




Today’s Topics







Summary


Summary

“High-Performance” Rooftop VAV System

High-efficiency rooftop

Evaporative condensing

Central relief/exhaust fan,rather than a return fan

Solar hot-water systemfor reheat

rooftop unit withevaporative condenser




“High-Performance” Chilled-Water System

Low flow, low temperature

Ice storage

Variable primary flow

High-efficiency chillers

Optimized plant controls

Waterside heat recovery

Central geothermal


Central geothermal


ExampleEnergy Analyses




Today’s Topics







Summary


Summary

large office building

Example Energy Analysis

“Baseline” chilled-water VAV system• Per ASHRAE 90.1-2007, Appendix G

• 55ºF supply air

“High-performance” chilled-water VAV system• 48ºF supply air (no downsizing of ductwork)

• Optimized VAV system controls (ventilation optimization, SAT reset)


• Parallel fan-powered VAV terminals

• Low-flow, water-cooled chiller plant



large office building

Example Energy Analysis (continued)

Active chilled beam (ACB) system Four-pipe active chilled beams

Separate primary AHUs for perimeter andinterior areas (with airside economizers)

Water-cooled chiller plant supplying the chilled beams

Separate low-flow, water-cooled chiller plant supplying the primary AHUs


8,000,000

10,000,000

12,000,000

rgy

Us

e, k

Btu

/yr

Pumps

Fans

Heating

Cooling


2,000,000

4,000,000

6,000,000

An

nu

al B

uild

ing

En

er Plug Loads

Lighting




small office building

Example Energy Analysis

“Baseline” rooftop VAV system• Per ASHRAE 90.1-2007, Appendix G

• 55ºF supply air

“High-performance” rooftop VAV system• High-efficiency, air-cooled packaged rooftop unit

• 52ºF supply air (no downsizing of ductwork)

• Optimized VAV system controls


Optimized VAV system controls (ventilation optimization, SAT reset)

• Parallel fan-powered VAV terminals

small office building

Example Energy Analysis (continued)

Variable refrigerant flow (VRF) system Heat recovery, air-cooled outdoor units

Packaged DX dedicated outdoor-air unitwith hot gas reheat




2 500 000

3,000,000

4,000,000

rgy

Us

e, k

Btu

/yr

Fans

Heating

Cooling


3,500,000

500,000

1,000,000

2,000,000

2,500,000

An

nu

al B

uild

ing

En

er Plug Loads

Lighting

1,500,000


Advanced Energy Design Guides

Funded by U.S. Dept of Energy

www.ashrae.org/freeaedg

Climate-specific recommendationsfor achieving 30% or 50% energy savings(envelope, lighting, HVAC, water heating)

Based on building energy simulations




Advanced Energy Design GuidesAEDG for Small or Medium Office Buildings

“High-performance” rooftop VAV systems are included as an option to achieve 50% energy savings

AEDG for K-12 Schools

Both rooftop VAV and chilled-water VAV systems are included as options to achieve 30% energy savings

AEDG for Small Hospitals and Healthcare Facilities


p

Both rooftop VAV and chilled-water VAV systems are included as options to achieve 30% energy savings

summary









References for This Broadcast

Where to Learn More


www.trane.com/EN

Watch Past Broadcasts

ENL Archives

Insightful topics on HVAC system design:• Chilled-water plants• Air distribution• Refrigerant-to-air systems• Control strategies• Industry standards and LEED• Energy and the environment• Acoustics• Ventilation• Dehumidification


www.trane.com/ENL



LEED Continuing Education Courseson-demand, no charge, 1.5 CE credits

ASHRAE Standards 62.1 and 90.1 d VAV S tand VAV Systems

ASHRAE standard 62.1: Ventilation Rate Procedure

ASHRAE 90.1-2010

Energy Saving Strategies for Rooftop VAV Systems

Air-Handing Systems, Energy and IAQ

Central Geothermal System Design and Control


Central Geothermal System Design and Control

Ice Storage Design and Control

www.trane.com/ContinuingEducation

2011 ENL Programs

MarchU di E i ti Chill d W t S tUpgrading Existing Chilled-Water Systems

JuneHigh-Performance VAV Systems

October Dedicated Outdoor-Air Units




Trane Engineers Newsletter Live program

Bibliography

Page 1 of 2

Industry Standards American Society of Heating, Refrigerating, and Air-Conditioning

Engineers (ASHRAE). ANSI/ASHRAE Standard 62.1-2010: Ventilation for Acceptable Indoor Air Quality. Available at www.ashrae.org/bookstore

American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). ANSI/ASHRAE IESNA Standard 90.1-2010: Energy Standard for Buildings Except Low-Rise Residential Buildings. Available at www.ashrae.org/bookstore

American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). ANSI/ASHRAE/USGBC/IES Standard 189.1-2009: Standard for the Design of High-Performance Green Buildings Except Low-Rise Residential Buildings. Available at www.ashrae.org/bookstore

Industry Articles, Papers, and Publications Advanced Energy Design Guides <www.ashrae.org/aedg>

American Society of Heating, Refrigeration and Air-Conditioning Engineers, Inc. (ASHRAE). 1996. Cold Air Distribution System Design Guide. Atlanta, GA: ASHRAE.

California Energy Commission (CEC). 2003. Advanced Variable Air Volume System Design Guide. Sacramento, CA: CEC.

Murphy, J. and N. Maldeis, “Using Time-of-Day Scheduling to Save Energy,” ASHRAE Journal 51(5), May 2009, pp. 42-48.

Stanke, D., “System Operation: Dynamic Reset Options,” ASHRAE Journal 48(12), December 2006, pp 18–32.

Stanke, D., “Single-Path Multiple-Zone System Design,” ASHRAE Journal 47(1) January 2005, pp 28-35.

Wei, G., Liu, M., and D. Claridge, “Optimize the Supply Air Temperature Reset Schedule for a Single-Duct VAV System,” Proceedings of the Twelfth Symposium on Improving Building Systems in Hot and Humid Climates, San Antonio, TX, May 2000.

Trane Application Manuals available to purchase from <www.trane.com/bookstore>

Murphy, J. and J. Harshaw. Rooftop VAV Systems, application manual SYS-APM007-EN, November 2009.

Murphy, J. and B. Bakkum. Chilled-Water VAV Systems, application manual SYS-APM008-EN, September 2009.

Murphy, J. and B. Bradley. Air-to-Air Energy Recovery, application manual SYS-APM003-EN, September 2008.

8 June 2011


Trane Engineers Newsletter Live program

Bibliography

Page 2 of 2

Trane Engineers Newsletters available to download from <www.trane.com/engineersnewsletter>

Eppelheimer, D. “Cold Air Makes Good $ense.” Engineers Newsletter 29-2 (2000).

Murphy, J. “CO2-Based Demand-Controlled Ventilation with ASHRAE Standard 62.1.” Engineers Newsletter 34-5 (2005).

Murphy, J. “Energy-Saving Control Strategies for Rooftop VAV Systems.” Engineers Newsletter 35-4 (2006).

Stanke, D. “Potential ASHRAE Standard Conflicts: Indoor Air Quality and Energy Standards.” Engineers Newsletter 37-4 (2008).

Stanke, D. “VAV System Optimization: Critical Zone Reset.” Engineers Newsletter 20-2 (1991).

Trane Engineers Newsletter Live Broadcasts available to view online at <www.trane.com/ENL>

Stanke, D., Schwedler, M., Taylor, S., and J. Harshaw, “ASHRAE Standards 62.1 and 90.1, and VAV Systems,” Engineers Newsletter Live broadcast (November 2008).

Murphy, J., Stanke, D., Lee, T., and M. Schwedler, “CO2-Based Demand-Controlled Ventilation,” Engineers Newsletter Live broadcast (November 2005).

June 2011


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